A Stable and Sensitive Engineering Bacterial Sensor via Physical Biocontainment and Two-Stage Signal Amplification.

Although engineering bacterial sensors have outstanding advantages in reflecting the actual bioavailability and continuous monitoring of pollutants, the potential escape risk of engineering microorganisms and lower detection sensitivity have always been one of the biggest challenges limiting their wider application. In this study, a core-shell hydrogel bead with functionalized silica as the core and alginate-polyacrylamide as the shell have been developed not only to realize zero escape of engineered bacteria but also to maintain cell activity in harsh environments, such as extremely acidic/alkaline pH, high salt concentration, and strong pressure. Particularly, after combining the selective preconcentration toward pollutants by functionalized core and the positive feedback signal amplification of engineering bacteria, biosensors have realized two-stage signal amplification, significantly improving the detection sensitivity and reducing the detection limit. In addition, this strategy was actually applied to the detection of As(III) and As(V) coexisting in environmental samples, and the detection sensitivity was increased by 3.23 and 4.39 times compared to sensors without signal amplification strategy, respectively, and the detection limits were as low as 0.39 and 0.86 ppb, respectively.

Portable ratiometric probe based on the use of europium(III) coordination polymers doped with carbon dots for visual fluorometric determination of oxytetracycline.

A novel ratiometric fluorescent probe for the determination of oxytetracycline (OTC) was developed. The method is based on the use of adenosine monophosphate/Eu(III) nanoscale coordination polymers doped with carbon dots (CDs) (CD@AMP/Eu NCPs). These were fabricated by self-assembly of Eu3+ and AMP on the surface of CDs containing large amounts of hydroxyl and carbonyl groups. Under the excitation at 310 nm wavelength, the doped NCPs display strong pink emission of Eu3+ at 615 nm and blue emission of the CDs at 430 nm on exposure to OTC. The ratio of fluorescence intensity (F615/F430) of such NCPs displays excellent linear relationship with OTC concentration ranging from 0.2 to 60 µM and the limit of detection (LOD) is 25 nM (3σ). The doped NCPs were evenly immobilized on common filter paper to prepare a visual ratiometric probe for the determination of OTC. Assisted by a digital camera with an APP color detector, the paper-based test strip was applied for the quantitative determination of OTC with a LOD of 0.5 µM and a wide linear scope of 1-100 µM. The method was applied to the determination of OTC in milk samples. Graphical abstractSchematic representation of the principle for oxytetracycline (OTC) determination using carbon dots (CD)@adenosine monophosphate (AMP)/Europium (Eu3+) paper-based ratiometic probe.

Polyethylenimine-Functionalized Corn Bract, an Agricultural Waste Material, for Efficient Removal and Recovery of Cr(VI) from Aqueous Solution.

In this study, polyethylenimine-functionalized corn bract (PEI-CB) was first used to remove aqueous Cr(VI) via the "waste control by waste" concept. The results indicated that PEI-CB had an excellent performance for Cr(VI) removal and the maximum removal capacity was 438 mg/g. The adsorption of Cr(VI) was fitted to the Langmuir model, and kinetics of uptake could be described by a pseudo-second-order rate model well. Amine was proven to be the active center for Cr(VI) adsorption and partial reduction to Cr(III), while removal efficiency was enhanced at a lower pH value and higher temperature. Besides, nanosized Cr2O3 with a high purity was obtained by simple calcination of a Cr(VI)-laden adsorbent. Hence, this study provided a novel strategy for Cr(VI) wastewater remediation and pure Cr2O3 recovery. Prepared PEI-CB was then a promising alternative of low cost for replacement of the current expensive absorbent of removing Cr(VI) from wastewater from the view of sustainability.

Dispersed conductive polymer nanoparticles on graphitic carbon nitride for enhanced solar-driven hydrogen evolution from pure water.

Developing new methods to improve the photocatalytic activity of graphitic carbon nitride (g-C3N4) for hydrogen (H2) evolution has attracted intensive research interests. Here, we report that the g-C3N4 exhibits photocatalytic activity for H2 evolution from pure water. And, the activity is dramatically improved by loading highly dispersed conductive polymer nanoparticles. The H2 evolution rate increases up to 50 times for g-C3N4 with 1.5 wt% polypyrrole (PPy) nanoparticles on the surface. The reaction proceeding in a pure water system excludes the need for sacrificial agents. The role of the highly conductive PPy in enhancing H2 evolution is as a surface junction to increase the number of photoinduced electrons, and to facilitate electron transfer to the interface.